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Analog univibe with DAC/digipots instead of LDRs?

PostPosted: 07 Dec 2017, 08:43
by vintagecharlie
Hi all,

While thinking about the univibe tones and seeing the LDRs, that are agood match for their builds, starting to be phased out, i thought, if it would be possible to substitute the lamp and ldrs with 4 digital pots or dacs and program them for what ever resistance sweep one would wish. Would this be feasible and doable? Has it been done in one of the modern mass produced units?

Would be interested in any input / feedback.

Best,

VintageCharlie

Re: Analog univibe with DAC/digipots instead of LDRs?

PostPosted: 09 Dec 2017, 13:29
by Dirk_Hendrik
If you have a digipot with enough steps. Yes.
However the first thing that strikes me is that this will be a device doing audio where there's some very active datacommunication lines (probably I2C or SPI) inside as well. That requires a very well thought of board layout or your noise floor will be pretty high.

Re: Analog univibe with DAC/digipots instead of LDRs?

PostPosted: 09 Dec 2017, 20:16
by vintagecharlie
The number of steps is crucial in order to have an analog-like smooth sweep, correct? Would a 10 bit pot be enough? Afaik that is the higher standard. Next thing that comes up on some google research is the “zipper noise” - can this be expected to be a problem in an application, where the resistor ladder will be switched up and down pretty fast and constantly? In my naive thinking a digi pot seems to be a perfect solution, but there must be a catch, if e.g. the univibe inventor himself simulated the circuit with a bazilion of transistors in the nuvibe, instead of going with digipots or dac. Btw. the nuvibe sounds great, similar to the original, but not the same as the ones that use bulb/ldr.